pinion sizes and options

[Chuck Keysor]

Hello Shopbotters of the world:
In looking to update my dear old Shopbot PRT alpha, I was told by Clearpath that I could use a NEMA 23 motor, instead of a NEMA 34 as came on my Shopbot. The output of my Oriental/VEXTA stepper motor is connected directly to the pinion that engages my rack. (There are no gearboxes on my legacy Shopbot.) My VEXTA output shafts are 14mm, with two orthogonal flats to engage the two set screws in each of my pinions. I had hoped to simply use my existing PRT alpha racks and pinions with a Clearpath motor and a gearbox.

The one planetary gearbox I have found that will provide a 14mm output shaft, is built to order and costs over $500 (each). YIKES.

Questions:

1)is it easy, or wise, to get an insert to reduce the internal diameter of my existing pinions down to 8mm and thus fit a standard NEMA 23 gearbox?
2) Are our Shopbot pinions common items, which can easily be purchased as standard items, but with an 8mm center hole instead of a 14mm shaft hole?

Sorry, I am an electrical person by training and experience. Mechanical things, while of interest, simply never fell into my work responsibilities or training....... so these may be dumb questions..... :confused: But I would really appreciate any information you can provide.

Thank you, Chuck

[jerry_stanek]

Have you tried Mcmaster Car

[ken_rychlik]

8mm seems very small for the loads you will have on it. 20 pitch and 20 degree pressure angle should be what you need. It was used on many different brand machines.

[Chuck Keysor]

Thanks Ken. Intuitively I had the same feeling as you about an 8mm shaft. Though I know my intuition is only that. But I am glad to know that 20 pitch teeth should be common. It is always helpful to know I am looking for something that may be a common item....... (I don't like looking for unicorns)... Thank you, Chuck

[Chuck Keysor]

Thanks Jerry. I had not checked them, but will do so,,,,,,,,, Thank you, Chuck

[Chuck Keysor]

Sure enough, McMaster-Carr has lots of gears/pinions........ Now figuring what is what is another matter, but here they are:
https://www.mcmaster.com/products/toothed-wheels/metal-gears-and-gear-racks-20-pressure-angle/?s=20+toothed+wheels

[ken_rychlik]

You can also check with boston gear

[Chuck Keysor]

Thank you Ken. I'll check with Boston Gear.

Not having a mechanical background, I had never heard of Boston Gear until a few weeks ago when someone recommended to me that I check with them as a source for buying new gearboxes as part of my Shopbot upgrade. (I did look at their site, and didn't find anything but stainless steel gearboxes.........)

Thank you, Chuck